The present invention relates to a monitoring apparatus for a pressure tank. Furthermore, the invention relates to a pressure tank comprising such a monitoring apparatus. The pressure tank is, in particular, a cryogenic pressure tank.
It is known from prior art to use cryogenic pressure tanks in vehicles. Prior art also includes systems for displaying the filling level of the cryogenic pressure tank. This is especially important when the vehicle can be operated with a fuel that is stored in the cryogenic pressure tank. A display system for the filling level of the cryogenic pressure tank is known, in particular, from DE 10 2012 205 887 A1.
It is therefore the object of the invention to provide a monitoring apparatus for a pressure tank, as well as a pressure tank, which with simple and cost-efficient production and assembly allow a safe and reliable determination for a filling level of the pressure tank.
This and other objects of the invention are attained by a monitoring apparatus for a pressure tank that is set up to determine the current operating parameters of the pressure tank. The monitoring apparatus is furthermore set up to calculate, using the operating parameters, a maximum possible filling level for the pressure tank if the current operating parameters are maintained. In particular, a quick removal of medium from the pressure tank leads to operating parameters that allow only a low maximum possible filling level. This is the case in particular with the use of heat exchangers that were used in the quick removal of the medium to introduce heat into the pressure tank. This can be calculated by the monitoring apparatus. Thus, it is taken into account in the scope of the invention, for example, that a possible refueling density of a pressure tank depends on the temperature and pressure in the pressure tank.
The monitoring apparatus advantageously includes a temperature sensor. The temperature sensor can record a temperature within the pressure tank as an operating parameter of the pressure tank. Alternately or in addition, the monitoring apparatus includes a pressure sensor. The pressure sensor can record a pressure within the pressure tank as an operating parameter of the pressure tank. If there were a high temperature and a low pressure in the pressure tank, the maximum possible filling level of the pressure tank is less than if there is a lesser temperature at the same or higher pressure inside the pressure tank.
Preferably, the monitoring apparatus furthermore includes a flow sensor that can record an outflow mass stream from the pressure tank as an operating parameter of the pressure tank. In particular, a long and continuous extraction from the pressure tank allows a high maximum possible filling level of the pressure tank. The outflow mass stream can be alternately calculated from a change of the pressure and the temperature within the pressure tank over time. The pressure and the temperature can be recorded with the aforementioned sensors, i.e. the pressure sensor and the temperature sensor.
The monitoring apparatus advantageously has a memory element in which a value for a best possible filling level for the pressure tank is stored. A best-possible filling level for the pressure tank has been achieved when the pressure tank is completely empty without executing any additional measures, in particular such as introducing heat into the pressure tank. This means that the best possible filling level has been achieved when the tank has a pressure that is less than a predefined swelling pressure and a temperature that is less than a predefined swelling temperature. Because the best possible filling level depends only on the pressure tank and its insulation quality, the best possible filling level can be stored in the memory element. If the monitoring apparatus, using the operating parameters of the pressure tank, calculates a maximum possible filling level that is lower than the best possible filling level, the monitoring apparatus can advantageously calculate a ratio of maximum possible filling level to best possible filling level. Thus, a user receives information as to which part of the maximum possible capacity of the pressure tank can be used.
So as to facilitate the forwarding of information from the monitoring apparatus to a user, the monitoring apparatus advantageously includes a display device. On the display device, in particular the maximum possible filling level and/or the best possible filling level can be displayed. Furthermore, it is preferably provided that a current filling level of the pressure tank can be displayed on the display device. Because the monitoring apparatus is set up to always calculate the maximum possible filling level using the current operating parameters for the pressure tank, a user of the pressure tank receives an immediate feedback about the effect of the current operation of the pressure tank. In the case that the pressure tank is installed in a vehicle and stores fuels for the vehicle, the user receives, from the display device and the monitoring apparatus, current feedback about its current driving behavior.
The invention furthermore relates to a pressure tank comprising a monitoring apparatus as described above.
The pressure tank preferably has a heating device, wherein thermal energy can be introduced into the pressure tank by the heating device. In particular, thermal energy can be introduced into the pressure tank when a pressure within the pressure tank falls below a predefined minimum pressure. The minimum pressure is necessary to ensure that a user is supplied with medium from the pressure tank. However, because the pressure within the pressure tank drops as the removal of medium from the pressure tank increases, the remaining pressure, once it falls below the minimum pressure, is no longer sufficient to properly supply the user. However, so as to be able to use the medium remaining within the pressure tank, the pressure within the pressure tank can be increased by use of the heating device. Increasing the temperature of the pressure tank simultaneously leads to a lesser maximum possible filling level of the pressure tank, which can be calculated by the monitoring apparatus. In particular, such a reduction of the maximum possible filling level because of the heating device can be calculated by the monitoring apparatus and displayed on the display device.
Advantageously, the heating device is a heat exchanger. Preferably, the heat exchanger can be connected to a cooling system of a user that can be supplied with the contents of the pressure tank. Especially preferably, the pressure tank is provided in a vehicle, wherein an engine or a fuel cell of the vehicle can be supplied by the pressure tank. Thus, the heat exchanger can be connected with a cooling system of the engine or the fuel cell. Because the temperature in the pressure tank drops, in particular, during a quick extraction of medium from the pressure tank, whereas the quick extraction simultaneously indicates a high performance requirement for the user, which is to say the engine or the fuel cell, the pressure tank provides a cooling capability when the user requires a cooling capability. In this way, on the one hand, the user can be cooled, and on the other hand, a pressure increase can be realized in the tank by introducing heat.
Especially preferably, the heating device can be activated or deactivated by a user via a user interface. As described earlier, it is in particular provided that the effects of introducing heat into the pressure tank by the heating device can be displayed to the user. Therefore, the user interface makes it possible for the user to make the decision whether or not the heating device is to be used. In particular when the pressure tank supplies a drive of a vehicle, the user can decide whether its vehicle is to have a large range with the current refueling or whether its vehicle is to have a large range with the subsequent refueling. If the heating device is not used, the entire supply cannot be extracted from the pressure storage. Therefore, the range of the vehicle is less then the maximum possible. However, if the heating device is used, the temperature inside the pressure storage increases. This means that the vehicle can be used for a greater range, but at the same time, the maximum possible filling level of the pressure tank decreases. Thus, during a new refueling, the pressure tank cannot be filled to the best possible filling level, which means that the range of the vehicle is less after a refueling.
The pressure tank is preferably a cryogenic pressure tank. The cryogenic pressure tank can, in particular, store hydrogen. The hydrogen is used in particular as fuel for a motor vehicle, with the motor vehicle having a fuel cell or a hydrogen engine.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawing.